Refers to a very small piece of matter, such as a grain of sand, a dust particle, or a subatomic particle. Used in both everyday and scientific contexts.
From Middle Chinese 粒子 (liX tsiX, 'grain, particle'). The kanji 粒 means 'grain' or 'drop', and 子 is a nominal suffix. The reading りゅうし is the Sino-Japanese on'yomi.
